Process for foaming around the peripheral edge area of cover for a motor vehicle roof and a motor vehicle roof cover

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for foaming around the peripheral edge area of a cover, especially a glass cover, for a motor vehicle roof, the cover being placed on or in a foaming tool and the foam mass being fed into the foaming tool such that two foam mass fronts are formed which run towards one another in the peripheral direction and merge with one another or meet one another in a merging area. The invention furthermore relates to a cover for a motor vehicle roof in which two foam mass fronts which are formed during the peripheral foaming in the foaming tool merge with one another in the merging area.

2. Description of Related Art

FIGS. 1 &amp; 2 schematically show a cover for a motor vehicle roof during or after peripheral foaming by means of a conventionally used process. The cover <b>10</b> is placed in a foaming tool in order to foam a carrier element <b>16</b>, which is usually called the “inside cover sheet,” to the bottom of the cover <b>10</b> and to provide for a peripherally foamed edge area <b>18</b>. In doing so, the foam mass, conventionally PUR, is added to the foaming tool from the sprue side <b>20</b>, resulting in the formation of two foam mass fronts <b>22</b> in the peripheral direction of the cover <b>10</b>, which fronts move towards one another in the peripheral direction of the cover and meet in an area <b>24</b> which is hereinafter called the merging area. Since ventilation takes place away from the peripheral area of the cover in the direction of the arrow <b>26</b>, in the form of the front <b>22</b> shown, i.e., when the flow rate on the ventilation side <b>26</b> of the foaming tool is greater than on the opposite boundary edge, there is the danger that, in the merging area, on the boundary edge of the foam mass facing away from the ventilation side <b>26</b>, air inclusions in the form of bubbles will occur. This area which is subject to bubble formation is labeled with reference number <b>30</b> in FIG. 2, which shows a section along the line II—II in FIG. <b>1</b>. These air inclusions cause a high scrap rate.

SUMMARY OF THE INVENTION

The primary object of this invention is to devise a process for foaming around the cover for a motor vehicle roof in which formation of bubbles due to air inclusions is prevented.

Furthermore, it is also an object to form a motor vehicle roof cover with an at least largely bubble-free foaming around the edge.

This object is achieved as claimed in the invention by a process in which the foaming tool is made such that, in the merging area, the foaming cross section on the side opposite the ventilation side of the foaming tool is reduced relative to the areas which border the merging area in order to prevent inclusion of gas bubbles in the merging area, and by a cover in which the cross section of the foam mass on the side opposite the ventilation side of the foaming tool is reduced relative to the areas which border the merging area. In this approach in accordance with the invention, it is advantageous that, especially by the corresponding configuration of the foaming tool, the probability of enclosure of gas bubbles in the foam mass in the merging area being pushed more towards the ventilation side of the foaming tool than in the areas adjoining the merging area.

Advantageous embodiments of the invention are explained in detail below by way of example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a prior art peripheral foaming process;

FIG. 2 is a sectional view along line II—II in FIG. 1;

FIG. 3 is a cross-sectional perspective view of a peripheral portion of a cover produced with the first embodiment of the process according to the invention, with the underside of the cover facing upward;

FIG. 4 is a section taken along line IV—IV in FIG. 3, the view being turned by 180° with reference to FIG. 3;

FIGS. 5 &amp; 6 are views corresponding to those of FIGS. 3 &amp; 4, but of a cover produced by a second embodiment of the process in accordance with the invention; and

FIGS. 7 &amp; 8 are views corresponding to those of FIGS. 3 &amp; 4, but of a cover produced by a third embodiment of the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Basically, foaming around a cover <b>10</b> in accordance with the invention takes place as follows: as in FIG. 1, the cover <b>10</b> is placed in or on a foaming tool (not shown) and the foam mass <b>18</b>, preferably PUR, is fed into the foaming tool such that two foam mass fronts are formed which run towards one another in the peripheral direction and merge with one another or meet one another in the merging area <b>24</b>. On the bottom of the cover <b>10</b>, which is formed preferably by a glass pane, as shown in FIGS. 3 &amp; 4, there is an inside cover sheet <b>16</b> which is made as a profile section and which has a bead <b>32</b> which runs in the peripheral direction, with a base <b>34</b> which adjoins the bottom of the cover or is connected to it by a cement/sealing bead <b>36</b>, a solar film or a sealing strip. As shown in FIGS. 3 &amp; 4, the outside edge area <b>46</b> of the bead <b>32</b> is completely surrounded by the foam mass <b>18</b> which attaches the inside cover sheet <b>16</b> to the cover <b>10</b>.

In the merging area <b>24</b>, with a center line indicated by reference number <b>38</b>, the foaming tool is made such that the structure or boundary of the foam mass <b>18</b> which is shown in FIGS. 3 &amp; 4 is formed in the merging area <b>24</b>. The ventilation direction of the foaming tool is indicated by the arrow <b>40</b>. Basically, the foaming tool is made such that, in the merging area <b>24</b>, the foaming cross section on the side opposite the ventilation side <b>40</b> is reduced relative to the corresponding part of the areas <b>42</b> which border the merging area <b>24</b>. Here, the “foaming cross section” is defined as the distance of the end of the foam mass from the peripherally foamed surface or the surface covered with the foam mass (this applies to the direction perpendicular to the plane of the cover) or the distance between the respective ends of the foam mass (this applies to the transverse direction, i.e., the direction which is located in the cover plane and which is perpendicular to the peripheral direction).

In the embodiment shown in FIGS. 3 &amp; 4, the foaming cross section diminishes, proceeding from the edge <b>54</b> of the merging area <b>24</b> to the middle <b>38</b> of the merging area <b>24</b>, on the one hand, in the direction perpendicular to the plane of the cover, and on the other hand, moreover, also in the direction transverse thereto, by which a recess area <b>44</b> is formed. According to FIG. 3, in the area <b>44</b>, the lower boundary of the foam mass <b>18</b> is gradually lowered towards the center line <b>38</b>, so that the covering of the bead edge <b>46</b> towards the center line <b>38</b> becomes thinner. Furthermore, the boundary of the foam mass of the recessed area <b>44</b> in the direction transverse to the center line <b>38</b> is pushed outward in the ventilation direction so that the area of the bead edge <b>46</b> which is covered with a thick layer of foam mass becomes narrower towards the center line <b>38</b>. In a plan view, this boundary line of the foam mass which runs in the peripheral direction is made S-shaped. The reduction in the foam cross section shown in the merging area <b>24</b> with the formation of the recessed area <b>44</b> results in that, in the peripheral foaming process, the flow rates of the flow fronts of the foam mass in the transverse direction, i.e., in the ventilation direction <b>40</b>, are made more uniform, reducing the danger of air inclusions and eliminating, so to speak, the area <b>30</b> shown in FIG. 2 which is subject to bubble formation. This effect is achieved by the corresponding geometrical configuration of the foaming tool which leads to the shaping of the foam mass <b>18</b> shown in FIGS. 3 &amp; 4.

The embodiment shown in FIGS. 5 &amp; 6 differs from the embodiment as shown in FIGS. 3 &amp; 4 essentially in that the recess, in the direction perpendicular to the plane of the cover, is made so deep that the area <b>50</b> of the bead edge <b>46</b> remains uncovered by the foam mass <b>18</b>. This shape is achieved in that the inner boundary <b>48</b> of the foam mass which runs in the peripheral direction is drawn in the ventilation direction <b>40</b> towards the center line <b>38</b> so strongly to the outside that the boundary line <b>48</b> is finally raised to the bead edge area <b>46</b>. In this case, the area <b>30</b> which is subject to bubble formation from FIG. 2 is left completely open.

In the embodiments shown in FIGS. 7 &amp; 8, for reducing the danger of bubble formation, not only does the foaming tool cooperate, but also the configuration of the inside cover sheet <b>116</b> itself does so. In this case the bead <b>132</b> is not made straight, as in the preceding embodiments, but it widens from the edge <b>154</b> of the merging area <b>124</b> facing the bordering area <b>142</b> towards the center line <b>138</b> of the area <b>124</b> in the direction to the ventilation side <b>40</b>, in a plan view an S-shaped configuration of the outer boundary line <b>152</b> of the bead bottom <b>134</b> arising. The foaming tool is made such that the foaming cross section decreases from the edge <b>154</b> of the merging area <b>124</b> towards its center line <b>138</b> in the ventilation direction <b>40</b>, i.e., the area covered with the foam mass <b>18</b> becomes narrower and narrower, the line of the inner boundary <b>148</b> of the foam mass following essentially the line of the boundary <b>152</b> of the bead bottom. In this way, in the merging area <b>124</b>, a part <b>150</b> of the bead bottom <b>134</b> remains uncovered by the foam mass <b>18</b>. The boundary <b>148</b> of the foam mass is made essentially S-shaped in a plan view. Here, like in the preceding embodiment, the area <b>30</b> which is subject to bubble formation is essentially completely eliminated or left open.

While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto. These embodiments may be changed, modified and further applied by those skilled in the art. Therefore, this invention is not limited to the details shown and described previously but also includes all such changes and modifications which are encompassed by the appended claims.